posted by john on .
A cheetah runs a distance of 102 m at a speed of 27 m/s and then runs another 102 m in the same direction at a speed of 34 m/s. What is the cheetah's average speed?
Average speed means total distance traveled divided by time. It is a average over time, not an average over distance.
Total time = 204/Vav = 102/34 + 102/27
2/Vav = 1/34 + 1/27
Solve for Vav
Vav = 2/[1/34 + 1/27] = 30.1 m/s
Note that it is not the average of 27 and 34.That would be 30.5 m/s.